apply dual timezone filters

closes: CNVS-9814

add support throughout our formatting layer
to give us a way to convert values
to the wall clock time of the timezone for
a course (or really any other way we choose),
and then apply that to several selected
date/time displays.

TEST PLAN:

- Login as a user who's part of a course
with at least some data in each tab
- Check the following areas to ensure that
the correct timezone-differentiated hover
text is showing up:
  * Announcements -> Date Sent column
  * Announcement Detail -> Date Sent (top right)
  * Assignments -> Due Date column
  * Assignment Detail -> Due Date (bottom table)
  * Collaborations -> Start Date
  * Discussions -> Last Post Date
  * Discussions -> Due Date
  * Discussion Detail -> Post date of each reply
  * Modules -> (if locked) shows date to unlock
  * Quizzes -> Due Date
  * Syllabus -> Dates on the left
  * Syllabus -> Due dates on the right
  * Settings -> Course Details -> start/end date
  * Settings -> Sections -> start/end date
  * Recent activity page -> Everything

Change-Id: I048c2de85d9f9b196d35c6c65ae104dab7441eee
Reviewed-on: https://gerrit.instructure.com/34861
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Drew Bowman <dbowman@instructure.com>
QA-Review: Steven Shepherd <sshepherd@instructure.com>
Product-Review: Ethan Vizitei <evizitei@instructure.com>